Pneumatic cushion



' July 27, 1943. M BREWSTER 2,325,223

PNEUMATIC CUSHION Filed Feb. 18, 1939 3 Sheets-Sheet 1 `Fuly 2.7, 1943.

M. l.. BREwsTl-:R .2,325,223 PNEUMATIC CUSHION Fi1ed"Feb- 18, 1959 Ilavlzfor:

5 Sheets-Sheet 2 July 27, 1943. M. l.. BREwsTEr-v PNEUMATIC CUSHIONlFiled Feb. 18, 1939 3 Sheets-Sheet 3 [22 u en Zal: MarshallLreawe/zPatented July 27, 1943 'u y, y2,325,223-l ,l

yprimat/mato oUsHIoN narshaunrevvster, vannuysgoaiir. AppncationFebruaryi, 1939, serial 1510.251217 ji e claims. u (C1. 15s-elimini' urIhis invention relates generally tov pneumatic cushions, and in itsprimary '.aspectis Vdirected particularly to the provision of apneumaticl cushion adapted fo-ruse in' aircraft and equipped with meansfor, automatically compensating lthe tendency of such a cushion tobecome unduly dis` tended and hard with increasing altitude-due tolowered external air pressure. However, while use, it is notnecessarilyv limited theretogsince it A municating with the vpresentinvention is chiefly directed to-sucli I involves features of advantagein point of -inf' creased riding comfort- When-employed inland vehiclessuch as automobiles'. Y

In aircraft service it is of course of the highest importance lthattheweight of allmembers be Undersea-level external pressure conditions,this compensating chamber remains substantially in a contracted,equilibrium condition, even whenthe cushion is loaded bythe weight ofthepassenger.

However, as the plane asc'ends andi-the external pressure falls, thedifferential of internal@ and external pressures exceeds a predeterminedmaximum limit,- at which-time 'the"compensating` chamber' expands andthereby increases the total Y volumetric capacity of the'cushion andchamber.I

, This-drops thefinternal pressuresufiiciently -to-l reduced to thebarest minimum consistent with structuralstrength'and the function to beful-` iilied. The weight of a `transport plane may-be materially reducedby -theuse of pneumatic' cushions An ordinary-pneumatic cushion, how-`ever,-is not well adapted to aircraft service,y -as 14* will be apparentfromthe following considera-- tions. If 4an ordinary air cushion :beinflated to a degree giving comfortablepsoftness at sea'level,

` the internal pressure will exceed the externalor atmospheric pressureby a degree which may be referred to as the normal pressure differentialnecessary to preserve or to give proper softness As thek plane ascends,the externalpressu're falls,

thus increasing this differential; and the cushion correspondinglydistendsl or becomes relatively restore, or preserve,the;"normaldifferential," zand: hence the desired degreeofsoftnessfl Theyield# ing restraint to .expansion imposed vby the elastic',VV

, compensating chamber walls limits'expansion 'atl all times to thatrequired to preserve,y approximately, or Within-'sufficiently closelimits, the' pre- 1 determined normal pressure differential.y v It fwill Y be apparentV that asthe plane' descends, and external pressureincreases, the' c'omp'ensttorIacts,l in effect, to decrease thevolumetric capacity-of the cushion,` ythus -raising the internal`pressure" and maintaining -the normal differential.

hard At high altitudes the' distension'is sunicient Ato make the cushionvery hard and 'uncomfortable, Y f w 'i t is accordingly'a primary objectof thepresent y invention to provide a pneumatic cushionffor use inaircraft, or other vehicles which encounter dif-f ferences in altitude,which will maintain'the dif'-A ferential ofinternal4 and'external'pr'essures aip-r proximately equal to a predetermined normalvalue for proper comfortthroughout the 'v range'r of barometric pressureconditions encountered in aircraft service.` Y

A further objectof the invention is to provide an extremely light seatlwhich Vis. comfortablev underall conditions incident toaircraft'service.

A still further object of the invention" is to provide an extremely`comfortable pneumatic cushion having improved shockl absorbing charLacteristics.

In accordance with the present invention, therev is, provided a Vlightframe Vwork equipped with cushion ofthe'seat of Figs".v 1 and 2; i

air `or gas-filled cushions. In aspecic illustrative form of theinvention, each of these cushions' has an expansive compensating chambercom-` i-Various additional features -of the'invention will appear-and beexplained in the; course fof 'the following description of typicalillustrative,'ern-Y l bodiments thereof.- Referencewill'be directedtoVthe accompanying drawings," in which:

` Fig. 1 isaside elevation of an aircraft seat em-k bodying thepresentinvention;

Fig; 3 is a Figurel is a section taken'as indicated by line Y Figi 5 is`an elevation,L with rparts broken away; of a modied form` ofcushion inaccordance with the present invention, being the seat of Figs. 1 and 2;

y Fig'. 5a is a'section taken Online 51145@ lof modifieations.l

its interior. In a present pre"- ferredform, this chamber embodies anelastic j sack or balloon, 'typically' lformed fof ljrubber.

plan View, with parts broken av'vay,v y of one illustrativev form ofcushionin accordanceI with the present' invention,- -being 'the bottomfthe yback cushion of Fig. 'lshowsa modified fom'ojf com'pelnsatorgiv Fias is a lschematic 'diagram showingrutner" mesma the volumetric capacity-of the v-gasholding enclosure. This expansion is sufficient to restore,or preserve, approximately, the fnormal'pressure differential? and hencethe required-.degree of 'cushion softness. With the use of .acompensating Vchamber havingelastic or resilientproperties, as a'rubbersack in the nature of a balloon, the tendency to expansion owingto increased pressure differential is of courseopposedby elasticityinherent the walls of the chamber, and it will' A:be apparent thatthe-resistance to expansion will become increasingly greater as thechamberex- `pands. This ofcourse means that the volumetric capacityofthe gasho'lding enclosure does l not increase linearly withdecreasinglexter-nal pressure; nevertheless, the increase in volumetric-capaci-ty -keeps 'pace with decreasing Iexternal pressure withcornparative closeness, andthe normal 4pressure differential establishedat sea level may for all practical purposes be regarded as approxi-V-mately preserved, i. e., confined within limits which are sufficientlyclose for the purpose, ioral'l normal iiight conditions.

`'lf-he expansion limiting external lbag $8` :limits expansion of rubbersack 3.50 against be-coming iing chamber 33. The size of this passagewayis` *large enough Asothat when-'the Weight of .the passenger issuddenlyirnposed on the cushion. either -ininitially sitting down, or incase ci shock Veither due 'rough airer in landing, theair will v flowfreely from cushion to compensating cham.- I iber, the latter ofcourse-expanding. The vrestric- -tion of the passageway is such,however, thatas the elastic chamber subsequently contracts, r.the

back flow of air, from elastic chamber to' cushion,y

-Will be somewhat checked, so' that sudden rebound is avoided. Thiseiect is due simply to -thefact caseszin whichfadjustment l'may not benecessary, the connecting passageway may :be vformed Aof ,the

i proper,nestrictedvcross sectional area .and the adfnstabile'valveiomitted. I v

' ably perforated `for lightness, asindicatedf'at615,-y

I. Figs. 1,2, 51andf6 vshowbacl: cushion i|2A 4to ,be l.madel up with.its internal .pneumatic cushion lill'in a-slightlymodied form. Inthis-instance :the internal cushion: ismade up ingrill form, comprisingl'upper and .lower horizontal members 16| and 62, respectively, andvspaced parallel members 63' joiningmembers 6l and 52, all of :saidVmembers vbeing of tubular cross section, lasshovvn in Fig. VVA6. 'Thepreferredmanner of :support 'of 'l Acushion iiILWh'ich may -also beemployed in .con-L nevction lwith previouslydescribed cushion `2,5; is vshown in -detail Fig. t.`r As ``.there shown,

cushion ='lill-restsagainst ametal plate `65, .preferysupported bytubular iframe worlrZi).y lIn the par.-

-ticular-construction-villustrated metal plate i65 isbentaround'tubularfrarne workflw and `fas Atened vvthereto 'as by`screws 61. A fabric memf f 2berLG8 is'placedbetween-metal platel and'frame "surrounds tubular iranie'work 2G, as wellfas, "cushion Eilandp'adding'l. y l,The princi-pal diferencebetween the forrnof `work 20,and wrappedaround saidfrarnefwork in themanner clearly illustrated `inFigi '6. Se-

1cured to this fabricinemberl are straps/1&9,

#which are cemented t'o-cushion- @El and support "thelat'terin--position against plate.

"Secured to'opposit'e sides of cushion iii), y:as/by Lcementing, arefabric sheets -l il, preferably formed oiballoon silk, #which is leituntreated iso that it `remains air-porous. Numeral ll `indicates usualfexterior upholsteryfand. numeral lf-2 the fion vfifi. illustrated,'upholsteryI r'lfl entirely Figs f5 'and 6 and that @ring-sys and 4 isthe that, with a restricted passageway between cusht ion andcompensating-chamber, the air will be forced with considerable velocityfrom cushion toward chamber under the pressure conditions existing whenthe load ofthe passenger is suddenly thrown von tl'iecusbion,y whereasthe back vflow of air `occurs simply by reason of the much 'weakerpressure rexerted by the stretchedwalls'of fthe compensatingchambenandhencesis atrmuch reduced velocity, so that the rebound .is checked.Theseat thus has the characteristics of apneudraulic shock absorber.This characteristic `of the lcushion renders it unusually comfortable,and because of the increased comfort provided, .the cushion may beemployed to advantage in land vehicles such as automobiles In suchservice,

Vno compensation for varyingfexternal pressure conditions is necessarilyinvolved, :but theshock absorbing functions of the cushion comeespecially v:into play Of course, While I have, here shcwna separat-e,:adjustable means in the form ofvalve -42 for adjusting the crosssectional area .of the passageway between cushiony 5 .and vthe. compen-`eating chambenit twill be -understoodvthaafin r,provision'in the-grillform ofligs and 6-of 'the spacesl "i5 between vertical cushion sections*'63, Vvwhich spaces 'l5 are utilized to' receive pressurevcompensatingu chambers. Thus, inthe embodi- `ment illustrated, lowercushion meinber- 62 is prt fvided, ,within eacnof spaces rc1, with aril-,tanger y'nipple `8l), over the end ofwhich is Aiitted-anfelonv4gated elastic compensating chamber'or sackfS'l,

`which"may *again be regarded v as j typically corn- 'posed of rubber,inthe nat-ure of ka rubberballoon Each of sacks lfil is lpro-vided withan expansion l 'limiting bag'or stocking itil, "formed of semel suitableflexible material such as cord mesh. This stocking is "fitted overjandmade secureto" nipple 280, for exampleas typically'in'dicated in Fig. 6.

'Cushionfil may be inflated-t rough valve fitting.

."Si'projecting vdownwardly'from the lower sidefc-f cushion section '62through upholstery ll.

The operation -of the formqof Figs. `5 and 16 is "the same asffthatpreviously described in connection with 'Figsj and 4. External airpressure conditions are transmitted through `tl'leeirtern'alupholstery"and'thrcugh'periorated plate G5 and lporous sheet "lli to thecushion-and to cornpensat'n f ing-chamber fSl." The compensatingcharnberor sackfinaexpanding, increases insize from its normal contractedcondition, .illustrated in full *lines inFigs.151and`6,tothe fullyexpanded limiting position indicated indottecl lines.` In yso--expanding'zsackffl 'moves upwardly in the form of `an :elongated"balloon`,.lir"ting mesh bag 82 with it,` and -ibcing /nally-,liinitedagainst further exv `parisienwhenfitj .has reached'zthe fullfdi arneteryflen'gth permitted by the dimensions of bag B2,

r,The forni lof vFigs. V5 `and 6 isvof .advantage Ain l:that @thecompensating chamberis entirely ,en-

light packing between said upholstery and cushf` .closed within vthelimits yor the ycushion itsemto obvious advantage.y i 'I i :f:

In Athelforms of the invention shown in Figs-c1 through 6, the yieldingrestraint-to expansion .of

the compensating chamberfisysupplied .by the useof an elastic,distensible wall. ...Of coursey the necessary yielding 'restraint andopposition to, eX- pans'ic-n of .thevv compensating chamber-,sommigebroadly considered', the increase. in the.vo1um.etric capacityof thegas-holding?.enclosure or system,

4maybe obtained in otherways.,` as Aby' use of,` a movable wallrestrainedagainst out.ward ..rnover ment by suitable' yieldableAopposing means/such as weight or spring. Fig.1 '7; shows such Va mQdiyiication; in whichr thev pneumatic cushion,. indi- 1 catedat963,;,connnunicates bywayof connection 9| with the head end. ofag-cylinderl .the latter .beingfitted with a movable Wall: 93 in theform of a piston, yieldinglyrestrained against outward movement by anelastic means in theform-of a compressionspring 95. Thishcompressionspring lacts between the wallorpiston 93 and asupport Aor seat ASiiformed on ytheendpfa stud 9 1 screwrthreaded lwithin a spiderS81;f1ountecl. within.the l openend-ofcylinder- 92.7. The headendcylinder is shown equipped 4with a ,valve fitting 9S,through whichthecushion may'qbe inflated. It will vbe evident that the form of Fig. 7 isthe full equivalent of the previously described form of the inventioninvolving a compensating chamber inthe form of an elastic sack, vthecompensating chamber in the instance of Figfi constituting the space Sdefined by the head of cylinder 92 andthe movable wall or piston 93,.the -latter corresponding,

of course, to thedistensible wall of sack 3S inthe seat 96 in a`direction longitudinallyf'of 'the' cylinder. 1, d l

.,Fig. 8 shows schematically a further modiiication which isillustrative of the use'of asingle compensating chamber for a `pluralityof cushions, and also of modified means for preserving the normaldifferential of internal and .external The system ofFig.. Sis cfa. dualythe pressure differential approximately constant. '.InFig.- 8, numeral|00" indicatesy pneumatic cushionsgwhich `for 4exanflple-may be lof.thetype f previously described. f f l nature,being-in realityillustative of two types oi I automatic means for maintaining the normalpressure diiferential` approximately constant.

VThus the system may be operated to pump the gas in reverse directionsbetween the cushions It mayV here be noted that while. Fig.

,buttwocushions |30-, `the system is of course in.-

`tended to operate in conjunction. with v,as-.many .cushionszas theremay bein use; in the aircraft. Communicating ,with the interior of thesef cushions; S @i vare connections "|51 joining with. a. .main gasconduit |532, thelatter leading `to .one side of ya reversible pump orcompressorrllkdriven byr'a reversible electric motor |05.,l `Rump. |04is of 4any suitabletype closing oil against reverse air lcwtherethroughwhen its operation is interrupte-d., The other side of pump |04.receives gas from ai line 1|05aleading. from a reservoir or accumulatorlilB, or-irom an intake-connection #d8-opening to atmosphere, dependingupon `the position of athreeway-valve |07.V When valve |01 is inposition to connect line |05 with the pump, intake |538 isof'course*closed,^.and vice versa. @jg f Joiningwith line |62 is aconnection IIB leading `tothe pressure side of aconventional type ofdiaphragm chamber and it' will be Aunderstood that the diaphragm `I 12erthis chamber is therefore-.exposed atall times to internal 'cush--ionpressure vTheopposite side of diaphragm v|l2..is; ,exposed toexternal ail'. pressure. Diaphragm-i i2 issupported against internalpressure by a spring ||3. Connected to the. diaplnagmis a shaft I4,carrying aswitch-operating member H5, which, ,under conditionswofL.normal 'pressurev differentialj standsvmidway between apair of.vswitches S1 and S2. 'When the pressure differential increasesabovewfnormalL diaphragmy l-Z moves against spring! I3 and carries.switch operating member ||5 in a direction to yclose vswitchhead S1, andwhen -the'pressure differential decreases below normal/7A diaphragm ||2.moves in the reverse'direction untilvswitch operating member H5l closesAapsecond switch Assuming control switch S3 to be closed andl acontrolswitch Sito beOpn-,gwithyalve llin position to connect reservoirm6 to pump |04, closure .of switch ySi resulting from increase in thepressure differential internally and externally of 'the vcushion, in.the manner described above, closes av .circuit energizing. Vmotor |05through leads |28) and |21, the circuit including aubattery or .sourceof' electrical energy KAS., This `causes :motor |l5 to drive insuchdirection as to operate pump H34 topump air or other gas froml cush-`ions |80 by way of line |ll2 to reservoir |06. I This operation resultsinv decreasing the pressure Idif.- Jfere'ntial internally and externallyof the cush- Y ions; and diaphragm I|2 accordingly returnsto and a gasreservoir or accumulator., under automatic control of means responsiveto .variations in in the differentialV of pressure internally andrei;-ternally of the cushions, in such a manner as to preserve saiddifferential approximately constant.

Or, by making certain changes,y the system may be operated, againunderthe control .of means responsive to the differential of pressures`internally and externally of the cushions, to'discharge air from' thecushions to atmosphere when the pressurel differential increases Vabovea' predetermined 4value, land to take air ,from-atmosphere and pump it.into` the cushions when the diner- 'entialagain decreases, all in amanner to hold its original position,k withdrawing Aswitchoperatingmember H5 from switch Si. The latteri thus opens, interruptingoperation of motor |05, and 4the system is againin equilibrium withthepressure differential internally andexternally of the cushions againVapproximately at normalwvalue. On theother hand, whenl the pressuredifferential'. decreases .below -normal value, diaphragm ||2.` moves"switch operating member ||5gin a manner to closeswitchSz. .Thisresults,A in clos,-

Singfanl energizing circuitto motor 0,5through lead |2|.and. a thirdleadv 122,. and the. motoris so-wired and arranged thatundersuch,conditions itrotates inthe reverse direction, and therefore drivespumpv |4.to pump air or gasy from reservoir Hllback to cushions |00.`When Ithe normal pressure differential is againsubstantially givenpassenger weightV to lowerl the internal cushion pressure in accordancewith lowered external air pressurethroughout a. normal altitude rangeofaircraft ilight. y

8, In-a pneumatic cushion for aircraft adapted `vtodbe self-compensatingto substantially maintain a predetermined internal pressure diileren-.tial over external air pressure for varying flight altiivmdes whileloaded with apassenger weight within a given passenger weight range, aflexible cushion casing adapted to be gas inflated, and

pressure compensating means associated withv .said casing substantially.inoperative in response to pressure-diiferentials Within the given rangeof passenger weights but operative under control of external airpressure in response torincrease in pressure differential to a higherrange caused by lowered external air pressure to lower the internalpressure in accordance withv the lowered .external pressure throughout anormal altituderange of aircraft flight. .-1 9. In a pneumatic cushionfor aircraftvadapted to be self-compensating to substantially maintain apredetermined internal pressure differential over external air pressurefor varying flight altitudes While loaded with a given passenger weight,

a flexible cushion` casing adapted to be gas in-.

iiated, and pressure compensating means assoelated with said casingembodying an expansive Vexternal pressure decrease throughout a normal20 altitude range of aircraft flight.

MARSHALL L. BREWSTER.

